This invention relates to optical communication systems. In particular, this invention relates to modulation, demodulation, transmission and reception of information in an optical communication system using an optical spectrum that includes the visible and invisible spectrum ranging from infrared to the ultraviolet light frequencies.
Existing optical communication systems modulate input signals onto light from a light source prior to transmission. For such optical communication systems, the light source typically provides coherent light that is narrowband and centred at a specific frequency.
To increase the capacity of information transmission in existing optical communication systems, a technique known as wavelength division multiplexing (WDM) is applied. In WDM, data is transmitted simultaneously on optical carrier signals at different wavelengths to increase transmission capacity. Thus, the transmission capacity of a WDM optical communication system is increased by a factor that is equal to the number of different wavelengths used.
However, WDM and other existing techniques such as time division multiplexing (TDM) to increase transmission capacity are still limited because each wavelength is modulated separately from the other wavelengths. Any unused capacity in one wavelength cannot be used to compensate overloading in another wavelength. Furthermore, the different wavelengths have to be provided by separate coherent light sources. For example, U.S. Pat. No. 5,729,369, issued to Zirngibl on Mar. 17, 1998 and assigned to Lucent Technologies Inc., describes the use of a multifrequency light source constructed of a plurality of distributed feedback lasers. Simplifying or eliminating the separate coherent light sources can therefore reduce complexity and costs of existing optical communication systems.
Therefore, a need clearly exists for an optical communication system that vastly improves transmission capacity.
In accordance with one aspect of the invention, there is disclosed a method for parallel modulation of an optical spectrum, the method comprising the steps of:
receiving the optical spectrum by at least one optical modulator, the at least one optical modulator being arranged in association with optical frequencies of the optical spectrum and coupled to at least one data signal source; and
simultaneously modulating, by the at least one optical modulator, a plurality of predetermined optical frequencies of the optical spectrum with a plurality of data bits provided by the at least one data signal source, each of the plurality of data bits being respectively coupled to the at least one optical modulator for parallel modulation of the plurality of data bits.
Optionally, the modulating step can comprise the step of amplitude modulating the plurality of predetermined optical frequencies.
Generally, the method can further comprise the step of synchronising operation of the at least one optical modulator with a spectrum controller for controlling the optical spectrum.
More generally, the method can further comprise the step of gating the optical spectrum at a predetermined frequency.
Alternatively, the method can further comprise the step of regulating the optical spectrum as pulses, each of the pulses having a predetermined period.
In accordance with another aspect of the invention, there is disclosed a method for parallel demodulation of an optical spectrum of modulated optical frequencies, the method comprising the steps of:
receiving the optical spectrum by at least one optical demodulator, the at least one optical demodulator being arranged in association with the modulated optical frequencies; and
simultaneously demodulating the optical spectrum, by the at least one optical demodulator, at a plurality of predetermined optical frequencies of the modulated optical frequencies to thereby derive a plurality of data bits, the plurality of predetermined optical frequencies being respectively demodulated in parallel by the at least one optical demodulator.
Generally, the demodulating step can comprise the step of detecting the optical spectrum at the plurality of predetermined optical frequencies.
Optionally, the detecting step can comprise the step of determining the amplitude of the optical spectrum at the plurality of predetermined optical frequencies.
In accordance with yet another aspect of the invention, there is disclosed an optical communication system for parallel modulation of an optical spectrum, the optical communication system comprising:
means for simultaneously modulating a plurality of predetermined optical frequencies of the spectrum with a plurality of data bits provided by at least one data signal source, the plurality of data bits being coupled to the modulating means for parallel modulation of the plurality of data bits.
Generally, the modulating means can comprise at least one optical modulator for controlling passage of the plurality of predetermined optical frequencies.
More generally, each of the plurality of data bits can be respectively coupled to each of the at least one optical modulator.
Optionally, each of the at least one optical modulator can comprise an optical switch.
Alternatively, each of the at least one optical modulator can comprise an optical shutter.
Generally, the optical communication system can further comprise means for synchronising operation of the modulating means with means for controlling the optical spectrum.
More generally, the controlling means can comprise means for gating the optical spectrum at a predetermined frequency.
Alternatively, the controlling means can comprise means for regulating the optical spectrum as pulses, each of the pulses having a predetermined period.
In accordance with a further aspect of the invention, there is disclosed an optical communication system for parallel demodulation of an optical spectrum of modulated optical frequencies, the optical communication system comprising:
means for simultaneously demodulating the optical spectrum at a plurality of predetermined optical frequencies of the modulated optical frequencies to thereby derive a plurality of data bits, the plurality of data bits being respectively demodulated in parallel by the demodulating means.
Generally, the demodulating means can comprise at least one optical demodulator, the at least one optical demodulator being arranged in association with the modulated optical frequencies.
Optionally, each of the at least one optical demodulator can comprise an optical amplitude demodulator.
Alternatively, each of the at least one optical demodulator can comprise an optical detector.
In accordance with a further aspect of the invention, there is provided an optical communication system for parallel modulation and demodulation of an optical spectrum, said optical communication system comprising:
means for simultaneously modulating a plurality of predetermined optical frequencies of said spectrum with a plurality of data bits provided by at least one data signal source, said plurality of data bits being coupled to said modulating means for parallel modulation of said plurality of data bits;
means for simultaneously demodulating said optical spectrum at a plurality of predetermined optical frequencies of said modulated optical frequencies to thereby derive a plurality of data bits, said plurality of data bits being respectively demodulated in parallel by said demodulating means; and
a communication medium.